Many electrical and electronic devices generate heat during operation and as microprocessors have gotten faster, their semiconductor elements have become smaller and more densely packed. The resulting increased amounts they generate of heat can lead to device failure and shorted lifetimes. Therefore, ever-increasingly more efficient methods of cooling semiconductor components are needed. Components such as heat sinks, heat conductive sheets, heat pipes, water coolers, fans etc. are often used to transfer heat away from its source. Heat sinks, for example, are often made from metals or ceramics having high thermal conductivities, but these can be bulky.
It would be desirable to be able to make cooling components from polymeric materials, as many such materials can be easily formed into a variety of shapes, including those having intricate designs, and a variety of sizes, including the very small sizes needed in many cases. Furthermore, since many housings for circuit boards and other components are made from polymeric materials, it would be desirable to be able to use thermally conductive polymeric materials for these applications, as the housing could then dissipate the heat generated by the electrical or electronic component, thus obviating the need for additional bulky heat sinks. However, in such applications it is frequently desirable that the polymeric material be electrically resistive (i.e., electrically insulating).
In order to obtain a highly thermally conductive resin, many thermally conductive polymer additives, such as ceramics, must often be used at high loadings, which can lead to increased costs and diminished physical properties of the resulting composition. Other additives such as graphite or carbon fibers can improve thermal conductivities when used in polymeric compositions, but can also increase the electrical conductivity of the compositions.
It would thus be desirable to obtain a polymer composition that is both thermally conductive and electrically insulating that that has good physical properties.
JP H06-196884 A discloses resin compositions comprising a filler (such as a metal, alloy, or ceramic) having a high thermal conductivity dispersed in a matrix resin. The composition further comprises a low-melting-point metal alloy. When an article comprising the composition is heated at a temperature at which the low-melting-point metal alloy is completely melted, the alloy is fused with the filler particles, cross-linking them.
JP 2003-301107 A discloses a composition containing 100 to 700 parts by weight metal oxide and 100 parts by weight of a resin mixture containing (a) 60-95 weight percent poly(arylene sulfide) resin and (b) 5-40 weight percent of an amorphous thermoplastic resin having a glass transition temperature of 140° C. or higher. The composition may further contain 15-100 parts by weight fibrous filler per 100 parts by weight of resin mixture. The composition has excellent thermal conductivity, low burring, excellent melt fluidity, and excellent heat resistance.
JP 2003-327836 A discloses a thermally conductive resin material containing carbon fibers and a matrix resin. The carbon fibers are formed by melting and spinning a mesophase pitch having specific properties and subsequently insolubilizing, carbonizing, and graphitizing the fiber. The composition has excellent moldability, mechanical performance, antistatic properties, and electromagnetic shielding properties.
WO 03/029352 and U.S. Pat. No. 6,995,205 B2 disclose a highly thermally conductive resin composition having a high thermal conductivity and good moldability. The composition comprises at least 40 volume percent of a matrix resin, 10-55 volume percent of a thermally conductive filler, and a metal alloy having a melting of 500° C. or less that binds the thermally conductive filler particles to each other. The volume ratio of the metal alloy and thermally conductive filler ranges from 1:30 to 3:1.